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Aminolevulinic Acid-Based Tumor Detection and Therapy: Molecular Mechanisms and Strategies for Enhancement

Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, PA 19104, USA
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Author to whom correspondence should be addressed.
Academic Editor: Michael R. Hamblin
Int. J. Mol. Sci. 2015, 16(10), 25865-25880; https://doi.org/10.3390/ijms161025865
Received: 16 August 2015 / Revised: 11 October 2015 / Accepted: 23 October 2015 / Published: 28 October 2015
(This article belongs to the Special Issue Advances in Photodynamic Therapy)
Aminolevulinic acid (ALA) is the first metabolite in the heme biosynthesis pathway in humans. In addition to the end product heme, this pathway also produces other porphyrin metabolites. Protoporphyrin (PpIX) is one heme precursor porphyrin with good fluorescence and photosensitizing activity. Because tumors and other proliferating cells tend to exhibit a higher level of PpIX than normal cells after ALA incubation, ALA has been used as a prodrug to enable PpIX fluorescence detection and photodynamic therapy (PDT) of lesion tissues. Extensive studies have been carried out in the past twenty years to explore why some tumors exhibit elevated ALA-mediated PpIX and how to enhance PpIX levels to achieve better tumor detection and treatment. Here we would like to summarize previous research in order to stimulate future studies on these important topics. In this review, we focus on summarizing tumor-associated alterations in heme biosynthesis enzymes, mitochondrial functions and porphyrin transporters that contribute to ALA-PpIX increase in tumors. Mechanism-based therapeutic strategies for enhancing ALA-based modalities including iron chelators, differentiation agents and PpIX transporter inhibitors are also discussed. View Full-Text
Keywords: aminolevulinic acid (ALA); protoporphyrin IX (PpIX); photodynamic therapy (PDT); tumor detection; fluorescence; heme biosynthesis aminolevulinic acid (ALA); protoporphyrin IX (PpIX); photodynamic therapy (PDT); tumor detection; fluorescence; heme biosynthesis
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Yang, X.; Palasuberniam, P.; Kraus, D.; Chen, B. Aminolevulinic Acid-Based Tumor Detection and Therapy: Molecular Mechanisms and Strategies for Enhancement. Int. J. Mol. Sci. 2015, 16, 25865-25880.

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